Thermometer



Feb. 16, 1932. BURGER 7 1,845,124

THERMOMETER Filed Oct. 12, 1929 INVENTO Patented Feb. 16, 1932 snitch STAT-Es PATENT oFFicE ALFRED Bun-GER, or noorrns'rnn, Yon-n, Assrenon r TAYLOR msritt mnnr COMPANIES, on Roorms'rnannw YORK, A oonroimrron'or NEW YORK 'rHEnMoMnrnn Application filed- October 12; 19293 serigum. 1399,24 1.

This invention relates to thermometers and has for its object means for magnifying the.

bore and more in particular the mercury thread.

Heretofore it was the general practice to lens the stem i. e. to provide a lens front to obtain the magnification.

In order to obtain a relatively large magnification, the lens front must form a very acute angle with the disadvantage that the field is very small, i. e. the-mercury thread can be seen only in a definite small range of positions of the eye relatively to the lens front. 1

Another difliculty militating against easy observation of the mercury thread is presented by the reflection of the light rays from the mercury as also from the'walls of the bore above the mercury. Since the medium within the bore above the mercury is less dense than glass, many of the light rays incident upon the bore are totally reflected into the'eye of the observer and thus materially impair the observation of the thread.

It is a particular object of the invention to provide a magnifying arrangement avoiding the above mentioned difficulties.

Briefly expressed, the invention comprises a magnifying lens within the body of the stem.

For a full understanding of the invention,

the principle upon which it is based,its preferred execution and its advantages, reference is made to the accompanying drawings wherein V Fig. 1 is a front elevation of a thermometer embodying the invention;

Fig. 2 is a cross-section thereof, on a larger scale, to more clearly show the characteristic aspect of the invention;

Fig. 3 is a cross-section of a slightly modified form of the arrangement shown in Fig. 2;

Fig. 4 is a cross-section of another form,"

. and

Fig. 5 is a cross-section of still another'embodiment. V t

In Fig. 1, 10 is the stem of a glass thermometer and 11 is the usual bulb connected ,mercury column 13 therein appear very wide relatively tothe stem, the apparent width being due to magnifying action obtained by the invention to be more fully described.

Having reference .to Fig. 2, the stem 10 is substantially semi-circular in cross-section and the flat side thereof is preferably provided with a coat 10a. of white enamel furnishing a light background. The capillary bore 12 is disposed in close proximity. to the fiat side andis preferablyovalj. In front of the bore 12 and symmetrically in respectto the center plane through the bore of the stem is disposed the relatively large channel 13. This channellwhich' constitutes the invention proper, defines two convex glass surfaces 14 and15opposing each other to forma collecting lens unit. As roughly indicated by the dotted lines, the rays of light emanating from the capillary bore in a forward direction, are all collected and refracted toward the medium plane, with the result that the image of the boreor the mercury correspondinglymagnified.

. The degree of magnification, of course, de-

column is tags that substantially all rays emanating from the borevwithin an angle of about 180 are collected and made useful for the visualization of the mercury. column. s In addition, light rays entering the stem cannot fall directly upon the bore or be reflected directly from the bore into the eye of the' observer. These rays, which heretofore constituted a great obstacle to a clear observation of the -mercury column, are now practicallyeliminated; as p a source of; trouble..- The mercury against a light background; In order to still.

more accentuate the idex;position of the mercury column, a colored, preferablyred stripe 16 maybeplaced to therear of the bore so to be'visually coextensive therewith.

.. I I1; Fig.13, the bore 22,,the channel 23 column is principally visible as a dark object tended for application in their correlation are substantially the same as described in connection with Fig, 2. However, the stem 20 has also a lens surface 2& which, although not as sharply defined as the usual lens front, has nevertheless a distinct magnifying action in addition to the action of the lens surfaces of the opening 23.

In Fig. 4, the'stem 30 is of the round form generally used before the lens front was known. The channel 31 is indicated as very much larger than in the forms abovedescribed. The size of the channel has no special relation to the particular form ofthe stem, but may be chosen, as in all other forms,

:to produce in conjunction with other factors affecting the degreeof magnification, the" desired effect.

In Fig. 5 is shown a form composed of "three parts separately manufactured and-subsequently united. The tubular part 40 re- I sembles the usual form of boiler .gauge tube, although proportionately smaller in crosssection,iand maybe provided with the enamel "coating lOa. Within the tube 40 are dis- :posed two glass'rods ll' and42 having curved surfaces 41a and 42a, respectively, approxi- 'mately fitting the wall of the inner wall of the tube and 'lenticular surfaces 41?) and 426,

:respectively, facing each other to 'form' the b'e connected, may bemanufactured in the usualway, aside from the peculiar shape of magnifying the bore.

In testimony whereof I afiix my signature.

ALFRED BURGER.

the stemand the parts may be readily united loy cement or the like. The top and bottom of the tube 40 may be closed to exclude dirt,

This'form of device has the advantagethat the scale which may be provided on the part is'not all essential. There is a great deal of latitude in-regard'to the structural detail of this form of the invention.

Although this invention is primarily inthermometers', it is'not limited thereto.

'I'claim: f

1. In devices of'the character described, a glass stem having a bore and a channel coextensive-in length with the bore, opposing faces of said 'channel being shapedto define 'a lens unit for visually magnifying the bore. 

